Grinding machine

ABSTRACT

The invention proposes a device for grinding or polishing workpieces by means of an abrasive, having a container and a rotary disk located therein and rotatable relative thereto, in which the rotary disk is made from elastic material, is provided with an upwardly directed rim and said rim has a finite spacing from the adjacent inner wall of the container.

[0001] Device for grinding or polishing workpieces by means of anabrasive, having a container (2) and with a rotary disk (3) locatedtherein and rotatable relative thereto.

[0002] Such devices are known in the form of centrifugal slidinggrinding machines, which comprise a two-part container with ashell-shaped, rotatable container lower part forming a bottom and astationary, cylindrical container upper part.

[0003] Such grinding machines are used for the surface machining ofgrinding articles, e.g. smaller parts and workpieces, which are moved inthe container together with the abrasive objects and optionally a liquidprocess medium. If the lower part is rotated, the workpieces to betreated are moved outwards on the disk until they encounter the innerwall of the container, where they are decelerated. A rotary workpiecemovement occurs as a result of the subsequently supplied workpieces andthis leads to an intense grinding or polishing action.

[0004] It is a disadvantage of such centrifugal sliding grindingmachines that the sealing of the annular clearance and the guidance ofthe faces bounding the same give rise to considerable problems, whichcan only be overcome with considerable effort and corresponding costs.

[0005] There is a danger that the upper and lower parts, particularlythe lower part, will be very greatly heated as a result of friction, ifparts of the grinding article and/or additionally added abrasive objectsduring operation enter the gap between the container bottom and therotary disk. This leads on the one hand to an only relatively shortregrind life of the grinding machine and on the other the latter must befrequently switched off during the machining of grinding articles inorder to prevent overheating both of the grinding machine and also thegrinding or polishing article.

[0006] DE 197 28 931 A1 discloses a liquid grinding machine for theliquid working of workpieces. A substantially planar elastic disk isprovided, whose radial extension exceeds the radial extension of thesurrounding container, so that on inserting the disk in the containerits flexible rim or edge is directed upwards and firmly engages on thecontainer wall, the compressive force being reinforced by thecentrifugal force during rotation of the disk. The liquid necessary forwet working is introduced into the container below the disk and underthe pressure overcoming the aforementioned application forces is forcedbetween the disk rim and container wall into the machining chamber. As aresult of considerable technical and constructional effort andexpenditure, a penetration of grinding material into the area below therotary disk is prevented, but in this form is only possible with wetmachining.

[0007] The problem of the invention is to provide a simply constructed,inexpensive device for polishing and grinding, whilst avoiding theaforementioned disadvantages, which in the case of limited wearsusceptibility functions reliably and has a long regrind life.

[0008] According to the invention, in the case of a device of theaforementioned type, this problem is solved in that the rotary disk hasan upwardly drawn, elastic disk rim and that the disk rim has a finitespacing from the adjacent inner wall of the container.

[0009] The finite spacing or gap, unlike in the case of DE 197 28 931A1, is constructionally determined by a radial minimum dimension of therotary disk with respect to the radial inside dimensions of thecontainer and consequently also exists in the inoperative state,particularly without the action of any external forces, such as occur inthe prior art as a result of the liquid forced through between the diskand the container wall. Thus, the elastic and in particular flexibledisk rim is not in contact with the container wall when the device is inthe inoperative state when the disk rim is not burdened by introducedmaterial. The invention deliberately takes into account the fact thatthe abrasive particles can pass between the disk rim and the containerwall, as well as between the disk bottom and the container bottom. Thisis counteracted by the centrifugal force exerted on such particles bythe rotation of the rotary disk and this leads to the particles beingdirected radially outwards below the disk bottom, which is aided by theelastic and preferably flexible underside of the disk bottom. As aresult of this and due to the elastic, flexible design of the disk rim,abrasive particles located between the latter and the container wall arereturned to the grinding chamber. A dynamic equilibrium of the materialflow occurs and there is always a certain mount of abrasive particles,which form an abrasion-reducing lubricant between the disk rim and thecontainer wall.

[0010] According to a preferred development, the disk rim tapers inpointed manner towards its free circumferential edge. As a result thedisk rim can be given a high flexibility, particularly in its outer,free edge region.

[0011] According to a highly preferred development, the disk rim isinclined outwards and has an inclination to the horizontal of less than90°, preferably between 30 and 70°. The (inner) opening or apertureangle of the disk rim to the horizontal is consequently between 150 and110°.

[0012] The size of the gap or the finite spacing of the disk rim fromthe container wall is preferably between 2 and 10% of the disk diameterand therefore, for conventional disk diameters of 15 to 40 cm, generallybetween 0.4 and 2 mm, preferably between 0.7 and 1 mm.

[0013] According to other preferred developments, the bottom of therotary disk substantially has a constant thickness, the disk rim havinga smaller thickness than the disk bottom or the outer circumference(towards the raised disk rim) of the disk bottom tapers.

[0014] It can be provided that the disk bottom thickness is betweenapproximately 2 and 8% of its diameter and that the rotary diskthickness is between approximately 5 and 10 mm.

[0015] The disk is also spaced from the container bottom. In a preferreddevelopment, the vertical spacing is between 1 and 2 mm. The gap widthcan in particular also be variable, so as to adapt the gap to thegranular material used. The adjustability of the gap can be madepossible by random known means, e.g. by a washer or the like placedbetween the container bottom and the disk and as a result a shaftpassing through the container bottom for the mounting of the flexibledisk can be vertically adjustable and fixed at a random height.Alternatively the container can be vertically adjustable with respect tothe disk and can be fixed in a desired height. According to a highlypreferred development, the size of the gap between the disk rim and thecontainer wall is smaller than the axial spacing from the disk to thecontainer bottom. This ensures that it is only possible for particles topass below the rotary disk which are much smaller than the spacing ofthe rotary disk bottom to the container underside.

[0016] According to a highly preferred development, in the transitionarea from the container bottom to the container wall, an increasedspacing is formed with respect to the rotary disk and in particular thecircumference of the disk bottom and which is in particular formed by anotch in the passage of the container wall towards the container bottom.This ensures that the rotary disk bottom, which is radially relativelyfirm, does not strike against the lower area of the container wall as aresult of thermal expansion. In the container wall notch it is possiblefor abrasive material to collect and this consequently guides thereturned, loose abrasive particles. As a result of its elasticity andthe abrasive particles acting as a lubricant there, a radial thermalexpansion in the vicinity of the disk rim is not critical.

[0017] It has been found that there is no increased heating underfriction and in particular no fusing takes place.

[0018] Besides the choice of a flexible material, this is also helped bythe shape of the circumferential rim, in that the latter is slender incross-section and pointed from the bottom area of the disk towards thefree edge or lip, so that assistance is also provided by the high lipflexibility.

[0019] According to a further development of the invention, the rotarydisk is made from plastic, particularly polyurethane. In a preferreddevelopment, at least the inside of the container and preferably theentire container is made from plastic, preferably polyamide 6 (PA6) orpolyamide 66, the Shore hardnesses of the materials preferably beingbetween 50 and 95°.

[0020] It has been found that such polyamides, particularly based onpolycaprolactam, constitute an optimum material for the container wall.In the case of standard abrasive materials or abrasives, the saidmaterial is not subject to any abrasion and wear. In addition, a fusingwith the rotary disk when suitable materials are used for the latter,once again polyurethane, is reliably prevented. As a result of the useof PA6, the self-cleaning effect of such abrasive parts which pass intothe gap and immediately are moved out again, is significantly improvedcompared with a PU-PU pairing.

[0021] The invention also relates to a grinding system with a deviceaccording to the invention for the polishing and grinding of workpiecesand with an abrasive having organic grains, the latter more particularlyconsisting of natural, organic material, such as walnut or coconutshell, wood, cherry stones, etc. or the abrasive grains consist ofsynthetic-organic material, particularly plastic. The abrasive ispreferably a composite abrasive with a central, organic material grain,which is surrounded by a binder layer containing polishing particles. Ina preferred development, the polishing grain composite has a centralwalnut grain, which is enclosed by a fat or wax layer, in which areincorporated polishing grains, particularly of aluminium oxide. Thisabrasive has proved to be of an optimum nature when used in a grindingmachine with a polyamide 6 casing and in particular also with apolyurethane disk, in order to on the one hand obtain good grindingresults and on the other to prevent damage of the grinding article orworkpiece and also the container wall and grinding disk, both throughthe otherwise occurring jamming and blocking of the drive. The abrasivegrain size can be between 50 and 500.

[0022] Another preferred development is characterized in that below thedisk in the bottom of the container is provided a closable outlet.

[0023] According to another highly preferred development, a drive axisof the grinding disk passes in liquid-tight manner through the containerbottom.

[0024] According to other developments, on the container and below thedisk is provided a rotary drive for the latter, whereby the axes of thedisk and the rotary drive are aligned.

[0025] This preferred development makes it possible to design a grindingmachine in a simple and inexpensive manner. This is helped by the factthat the disk is connected in bearing-free, non-rotary manner to thedriven shaft of the rotary drive. Through this preferred solution thereis no need to provide a separate bearing for the driving shaft of therotary disk in addition to the bearing for the driven shaft of therotary disk, where the latter may be a driving motor or a geared motorwith integrated motor and integrated gear. According to a preferreddevelopment, the disk is connected by means of a coupling to the drivenshaft of the rotary drive and in particular the coupling has alignedbores. which carry the driven shaft of the rotary drive and a centringpin for the disk. The coupling and the driven shaft are connected innon-rotary manner by a radial clamping bolt. The rotary disk andcoupling are interconnected in non-rotary manner by means of screws.There is a dust-tight and/or liquid-tight passage of the disk drivethrough the container bottom and the coupling is in particular heldfirmly in the containers by retaining rings, so that an optimum sealingaction is obtained.

[0026] According to other developments of the invention, the rotarydrive is held in a foot or base part and firmly connected thereto byscrews and the fastening screws for the rotary drive are orientedparallel to the axis.

[0027] The casing is preferably in one piece and in particular thecasing and/or container is made from plastic. As a result the grindingmachine according to the invention can be manufactured economically andtherefore inexpensively. This is helped by the fact that the gear isplaced below the disk. In an alternative development, the drive isconstructed as a geared motor with an integrated drive and then inparticular the motor is vertically oriented with its axis and a drivingshaft passes out at the lower end of the motor.

[0028] As a result of the construction of the device or grinding unitaccording to the invention, a machine can be provided with severalgrinding units at limited cost, so as to e.g. permit the rationalmachining of heavier and/or shock-sensitive workpieces, which do notallow a common machining of several workpieces in a single container. Infact, a large number of units can be provided, e.g. more than 30. Thedisks of the individual containers can either be separately driven orthe grinding machine has a common drive for all the units. In the lattercase the disks of the units in each case located on one shaft can beconnected by coupling elements, such as meshing gear wheels, V-belts,etc., to the central drive and the disks of individual containers canpreferably be separated uncoupled from the central drive, so that duringthe grinding of workpieces in certain containers of the grindingmachine, the other containers can e.g. be cleaned or emptied and thenagain filled with workpieces. A grinding machine according to theinvention can in particular be used for the dry polishing of jewellery,dental parts, etc.

[0029] Further advantages and features of the invention can be gatheredfrom the claims and the following description of an embodiment of theinvention and with reference to the attached drawings, wherein show:

[0030]FIG. 1 A preferred development of a device according to theinvention.

[0031]FIG. 2 Another development of a device according to the inventionin side view.

[0032]FIG. 3 The essential parts of the device of FIG. 3 (sic) invertical section.

[0033]FIG. 4 A larger scale view of the region of the circumferentialrim of the rotary disk.

[0034]FIG. 5 A larger scale detail of the rotary disk and container of adevice according to the invention.

[0035]FIG. 1 shows a preferred development of a device according to theinvention, which has a simple construction and which can therefore bemanufactured at limited cost and offered for sale at a low price, sothat it can also be used in the private sector for polishing privatejewellery articles.

[0036] The device 1 of FIG. 1 of a centrifugal sliding grinding machinein the form of a disk centrifugal machine has a container 2 with arotary disk 3.

[0037] According to FIG. 1, the device 1 has a one-piece casing 2′ witha container 2 and a foot or base 2″. The casing 2′ is here made fromcaprolactam, with NH(′CH₂)₅CO chains and said material is conventionallyalso referred to as polyamide 6 or PA6. The container 2 is made fromthis material. In the container 2 is located a rotary grinding disk 3.The rotary disk 3 is made from flexible material, such as relativelysoft plastic or rubber and in particular polyurethane. The grindingmaterial is a polishing grain composite with a central grain of organicmaterial with a wax or fat layer in which the polishing granules areincorporated. The organic material can be natural material, such aswalnut shell, cherry stones, wood, coconut shell, etc., as well as asynthetic material such as plastic.

[0038] The rotary disk 3 has a circumferential rim 31 which is drawnupwards and which is inclined outwards, whose outer wall follows thecontour of the container in this area and is consequently parallelthereto. Thus, between the disk 3 and container bottom 2 a is formed afinite spacing 5 with a size b of approximately 1.5 mm, which over theentire disk surface has essentially the same size. The disk and/orcontainer 2 can e.g. be vertically adjustably positioned whilst varyingthe gap width b. As a result of the upwardly drawn disk rim 3 a, adisk-like receptacle for the grinding article is created. Between thedisk rim 3 a and the container wall 2 b is formed a gap 5 a, which issmaller than the spacing 5 and has a width of approximately 0.8 mm.

[0039] In the foot 2″ below the rotary disk 3 is provided a rotary drive11 for the latter. The rotary drive can be a motor directly driving therotary disk 3 or a geared motor with an integrated gear. The rotarydrive 11 has a vertically upwardly directed driven shaft 12. The rotarydrive 11 is fixed by means of screw connections 13 directed parallel tothe shaft 12 and a mounting plate 14 to the casing 2′. A bore of thecasing 2′ between foot 2 a and container 2 contains a coupling 15, bymeans of which the rotary disk 3 is connected in non-rotary manner tothe driven shaft 12 of drive 11. For this purpose the coupling 15 hasbores 15 a, 15 b. Into the bore 15 a projects the driven shaft 12 ofdrive 11. A radial clamping bolt 16 is provided for non-rotaryconnection purposes. Into the bore 15 b projects a centring pin 17,which is firmly connected to the rotary disk 3. A non-rotary connectionbetween the rotary disk 3 is brought about by screws engaging in thecoupling 15 parallel to the centring pin 17.

[0040] The axis A of the rotary disk 3 and rotary drive 11 is aligned.The bores 15 a, 15 b can also be in the form of a through bore. Belowthe coupling 15 the driven shaft 16 of the rotary drive 11 is surroundedby a centring ring 19. In the upper area of the coupling, a hardenedring 21 is firmly connected thereto. The coupling 15 is axially retainedin the casing 2′ by retaining rings 22.

[0041] As stated, the rotary disk 3 is spaced from the container bottom2 a, accompanied by the formation of a gap 5.

[0042] During the operation of the grinding machine the comparativelywide gap makes it possible for small particles of the grinding productor in particular the abrasive to pass between the rotary disk 3 and thecontainer bottom 2 a and as a result of the rotating, flexible disk theyare again passed in the direction of the container wall without therebeing any significant wear to the container bottom 2 a or rotary disk 3.

[0043] As a result of the flexible rotary disk 3 the generation offrictional heat is largely prevented, in that abrasive particles whichget under the rotary disk 3 are not crushed and instead are movedradially outwards. In addition, it is possible to provide laterally inthe bottom 2 a of container 2 a closable outlet 22, which is closedduring operation and by means of which any grinding material which haspassed below the disk 3 can be removed when the grinding unit hasstopped.

[0044]FIGS. 2 and 3 shows a further development of the invention, inwhich the grinding machine according to the invention once again has asimple construction and is therefore inexpensive to manufacture.

[0045] In this case the casing 2 a has a foot 2 c, which is notconstructed in one piece with the container 2. In a manner which has notas yet been explained the container 2 is fixed to the foot 2 c. In thiscase and as is in particular visible in FIG. 3, a motor 11 is positionedlaterally of the container 2 and the foot 2 c in such a way that thedriven shaft of the motor, which is not itself shown, passes outdownwards from the motor 13. The gear 12 is also located below the motor13 and the drive 11 can also be constructed as a geared motor 14. Thetop of the motor 13 is essentially at the same height as the upper edgeof the container 2.

[0046] Below the rotary disk 3 in container bottom 2 b there is onceagain a closable opening 15, by means of which any grinding materialwhich has passed below the disk 3 can be removed.

[0047]FIG. 3 makes it clear that in the foot 2 c of casing 2 is provideda U-shaped bracket 17, whose leg is fitted to the foot 2 c of casing 2′and which carries the container 2 with its crosspiece. A drive axis 3 bfor the disk 3 passes through the bottom 2 b and the crosspiece of thebracket 17 into the gear 12, which extends from its parts immediatelybelow the motor 13 to centrally below the container 2, in thatcorresponding idler gears or other gear designs such as tooth belts,etc. are provided.

[0048]FIG. 4 shows a detail of the upwardly drawn circumferential rim 31of the rotary disk 3 rotatable about axis A in container 2. In therepresented embodiment, at least the circumferential rim 3 a is madefrom a flexible material with a Shore hardness of 50 to 95°. The rotarydisk or its bottom 3 b can be made from the same or a differentmaterial. Additionally or alternatively, in the vicinity of thecircumferential rim 3 a, the container wall 2 b can be flexible orelastic.

[0049] The circumferential rim 3 a tapers from the bottom area 3 b ofthe disk 3 to the free edge 3 c thereof. The opening angle α of thecircumferential rim 3 a to the bottom 3 b is approximately 150° in theembodiment shown. The angle β between the underside 3 d of the bottomand the outside 3 e of the circumferential rim 3 a is accordinglyapproximately 130°. The value for both angles α, β is preferably between105 and 150°. The inclination 8 of the container inner wall in thevicinity of the rotary disk and therefore the outside of thecircumferential rim of the rotary disk 3 in each case to the horizontalis generally between 30 and 70° and is here 65°.

[0050] When the rotary disk 3 is unloaded, i.e. when the latter does notrotate and centrifugal forces are not exerted on the circumferential rim3 a and the latter, particularly in the edge region 3 c does not contactthe inner wall 2 b of the container 2, it instead has with respectthereto a finite spacing or gap 5 of at the most preferably 0.4 to 2 mm.Between the underside 3 d of the rotary disk 3 and the top 2 c of thebottom 2 a of container 2, there is also a gap 5 a or finite spacing.

[0051] Another preferred development of the invention can be gatheredfrom FIG. 5 showing in detail form parts of the container 2 and rotarydisk 3, the reference numerals coinciding with those used hereinbefore.The angle between the inner wall 2 b of the container in the vicinity ofor level with the rotary disk 3 with respect to the angle and which isdesignated γ is here 55°. Unlike in the previously describedembodiments, in the lower region of the inclined wall 2 b of container 2there is a recess 2 i, whose height is roughly determined by thethickness of the bottom 3 b of the rotary disk 3. The recess 2 i isbounded by a horizontal bottom area 2 j and a vertical wall area 2 k.This recess prevents any pressing of the lower, radially less flexiblearea of the bottom 3 b pressing against the wall 2 b of the container 2as a result of thermal expansion of the disk 3, so as to bring about inoperation a significant heat generation and wear. If the upper edgeregion of the lip of the raised rim or the lip of the rotary diskcontacts the wall 2, as a result of the flexibility of the raised rimthis causes no problems, because as a result of the organic nature ofthe abrasive material used, an antifriction layer of the same materialand wax surrounding the corresponding grains is provided, so as to exerta friction-reducing action. In the vicinity of the recess 2 i abrasivematerial (organic material such as walnut particles and embedding wax)collects and extends roughly up to the broken line 21 shown.

[0052] Workpieces and abrasive agents are shown in small numbers inexemplified manner and for machining the container of FIG. 1 is filledto a significant extent with an abrasive (at least one third filled).The abrasive 20 for grinding the workpieces 21, such as e.g. jewelleryrings, is a composite abrasive based on walnut granules having a centralwalnut grain 22, which is externally surrounded by a fat or wax layer,in which are incorporated abrasive polishing grains 24, particularly ofsilicate or oxide.

[0053] When the disk grinding machine 1 according to the invention is inoperation, the free edge 3 c of the circumferential rim 3 a of theabrasive disk 3 is pressed by centrifugal force and the abrasivematerial 20 and grinding article (workpieces) 21 filled into thecontainer against the wall 2 b of said container 2, so that entry ofwalnut abrasive into gaps 5, 6 is largely prevented.

[0054] During machining the polishing grains become worn, so that dustand abrasive particles occur and in addition resinified wax and fatconstitutes also form dust. Such dust and abrasive particles which aresmaller than the actual abrasive agent 20 are able to pass between thedisk rim 3 a and the container wall 2 b and pass below the container andas a result of the flexibility of the circumferential rim 3 a (andoptionally to a lesser extent the wall 3 b), due to the centrifugalforces acting thereon due to the rotary disk movement, they are again inpart forced through the marginal gap 5 a into the machining chamber. Inpart they can be removed through an outlet in the container bottom.

[0055] It has been found that the material combination polyamide 6 forthe container, or at least the inside of the container, and polyurethanefor the actual container is of an optimum nature, particularly inconjunction with the aforementioned abrasive. There is no wear to thecontainer wall. As a result of this choice of material, fusing betweenthe rotating disk and container wall in the case of contacts caused bycentrifugal forces is prevented. This would occur through the heatingcaused by friction if e.g. the disk and container bottom were made fromthe same plastics material. In addition, the self-cleaning effect issignificantly improved.

[0056] During the operation of the disk grinding machine according tothe invention, particularly in the case of a dry process, the free edge3 c of the circumferential rim 3 a is pressed by centrifugal force andthe abrasive material and grinding product filled into the containeragainst the wall 2 b of said container 2, so that entry of abrasivematerial into gaps 5, 6 is largely prevented. However, as a result ofthe flexibility of in particular the circumferential rim 3 a (or alsothe wall 2 b), the abrasive grains can be forced out of the gap againthrough the centrifugal forces acting thereon due to the rotary diskmovement. Despite the contact between the circumferential rim 3 a andthe container wall 2 b, there is surprisingly no excessive heating ofthe disk and in particular the circumferential rim 3 a, which isnormally made from PU, and in particular no fusing with thecircumferential wall as a result of heating. This may be due to the factthat as a result of the abrasive powder or dust formed enters the gap 5between the circumferential rim 3 a, particularly in the vicinity ofedge 3 c and container wall 2 a and exerts a lubricating action there.

1. Device for grinding or polishing workpieces by means of an abrasive,having a container (2) and a rotary disk (3) located therein androtatable relative thereto, characterized in that the rotary disk (3)has an upwardly drawn, elastic disk rim (3 a) and that the disk rim (3a) has a finite spacing from the adjacent inner wall (2 b) of thecontainer (2).
 2. Device according to claim 1, characterized in that theoutside of the disk rim (3 a) has an inclination (angle γ) of less than90° to the horizontal.
 3. Device according to claim 2, characterized inthat the inclination to the horizontal of the outside of the disk rim (3a) is between 30 and 70°.
 4. Device according to claim 1 or 2,characterized in that the outside of the disk rim (3 a) and the innerwall (2 b) of the container (2) are substantially parallel to oneanother.
 5. Device according to one of the preceding claims,characterized in that the finite spacing or gap (5) at the upper, outeredge of the disk rim (3 a) with respect to the container inner wall (2b) is between approximately 2 and 10° /°° of the diameter of the disk(3).
 6. Device according to one of the preceding claims, characterizedin that the finite spacing or gap (5) at the upper, outer edge of thedisk rim (3 a) of the container inner wall (2 b) is betweenapproximately 0.4 and 2 mm of the diameter of the disk (3).
 7. Deviceaccording to one of the preceding claims, characterized in that the diskrim (3 a) tapers towards its upper, free edge.
 8. Device according toone of the preceding claims, characterized in that the disk bottom (3 a)is made from elastic material.
 9. Device according to one of thepreceding claims, characterized in that the free spacing between thedisk rim (3 a) and the adjacent inner wall (2 b) of the container (2) issmaller than a vertical spacing between the underside of the disk bottom(3 b) and the top (2 c) of the container bottom (2 a).
 10. Deviceaccording to one of the preceding claims, characterized in that thebottom (3 b) of the rotary disk (3) substantially has a constantthickness.
 11. Device according to one of the preceding claims,characterized in that the disk rim (3 a) has a smaller thickness thanthe disk bottom (3 b).
 12. Device according to one of the precedingclaims, characterized in that the outer circumference (towards theraised disk rim (3 a)) of the disk bottom (3 b) is tapered.
 13. Deviceaccording to one of the preceding claims, characterized in that thethickness of the disk bottom (3 b) is between approximately 2 and 8° /°°of its diameter.
 14. Device according to one of the preceding claims,characterized in that the thickness of the rotary disk (3) is betweenapproximately 5 and 10 mm.
 15. Device according to one of the precedingclaims, characterized in that in the transition area from the bottom (2a) of the container (2) to the wall (2 b) thereof, an increased spacingwith respect to the disk is formed.
 16. Device according to claim 15,characterized in that the increased spacing is formed by a notch (2 i)in the path from the container wall (2 b) to the container bottom (2 a).17. Device according to one of the preceding claims, characterized inthat the rotary disk (3) is made from plastic, particularlypolyurethane.
 18. Device according to one of the preceding claims,characterized in that at least the inside of the container andpreferably the entire container is made from plastic, preferablypolyamide 6 (PA6) or polyamide
 66. 19. Device according to claim 17 or18, characterized in that the flexible areas of the disk (3),particularly the disk rim (3 a) is made from or lined with materialhaving Shore hardnesses between 50 and 95°.
 20. Device according toclaim 18 or 19, characterized in that at least the inner wall of thecontainer (2) and preferably the entire container is made frompolycaprolactam.
 21. Grinding system with a device for grinding orpolishing workpieces according to one of the preceding claims,characterized in that abrasives with an organic grain are used. 22.Grinding system according to claim 21, characterized in that the grainof the abrasive comprises natural, organic material, such as walnut orcoconut shell, wood, cherry stones, etc.
 23. Grinding system accordingto claim 21, characterized in that the abrasive grain comprisessynthetic-organic material, particularly plastic.
 24. Grinding systemaccording to one of the claims 21 to 23, characterized in that theabrasive is a composite abrasive with a central grain of organicmaterial, which is surrounded by a binder layer containing polishingparticles.
 25. Grinding system according to one of the claims 21 to 24,characterized in that the grain size of the abrasive is between 500 and50.